Airplane dispatching system



March 21, 1944.

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March 21, 1944.

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S. N.W]GHT AIRPLANE DISPATCHING SYSTEM Margh 21, 1944.

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AIRPLANE DISPATCHING SYSTEM Filed Feb. 24, 1942 15 Sheets-Sheet 8 FIG.2C.

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' ATTORNEY March 21, 1944.

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AIRPLANE DISPATCHING SYSTEM Filed.Feb. 24, 1.942 13 Sheets-Sheet l0March 21, 1944.

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AIRPLANE DISPATCHING SYSTEM Filed Feb. 24, 1942 13 Sheets-Sheet 11FIG.2.F. I z

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TTORNEY March 21, 1944.

s. N. WIGHT 2,344,759 7 AIRPLANE DISPATCHING SYSTEM Filed Feb. -24, 194215 Sheets-Sheet 12 Mmh 21, 1944.;

N. WIGHT AIRPLANE DISPATCHING SYSTEM m1ea.;eb. 24, 1942f 1s Sheets-Sheet1s HRNQN Ovm ATTORNEY Patente d Mar. 21, 1944 UNITED AIRPLANEDISPATCHING SYSTEM Scdgwick N. Wight, Rochester, N. Y., assignor toGeneral Railway Signal Company, Rochester,

Application February 24, 1942, Serial No. 432,121

18 Claims.

The present invention relates to airplane dispatching. The inventionmore particularly relates to apparatus for making a visual record ofcommunicated instructions, acceptance of these instructions and theprogress of planes, .over routes authorized by these instructions whichapparatus includes electrically interlocked circuits to prevent thegiving of conflicting instructions and to prevent the cancellation ofaccepted instructions.

Commercial passenger and mail transport planes under present practicefly over ground routes which are defined by radio beams which define thepath of travel over the earth but do not in any way define the altitudeat which, the plane or planes may fly. These radio beams do notconstitute part of the present invention except in that they are anecessary aid for blind flying, that is, flying in fog, 0. 7 which thepresent airplane dispatching system, has been particularly devised. Forpurposes of simplicity the present invention has only been shown appliedto two different routes which extend primarily in an east-west directionand which routes cross each other at an intermediate location. Inaccordance with the present invention it is contemplated that alleastbQ11 nd planes over both routes fly at odd altitudes of 3000, 5000,7000 and 9000 foot elevations and which permit westbound planes to flyat even altitudes of 2000, 4000, 6000 and 8000 foot elevations. Inaddition to these altitudes it is proposed to allow, so called, freelance flying below a 2000 foot elevation and to allow similar free lanceflying at stratosphere elevations above, say, an 18,000 foot elevation.Between the 9000 foot route illustrated and the 18,000 foot stratosphereelevation mentioned it is proposed to have additional even thousand footelevations for West -abound dying and odd thousand foot elevations foreast-bound flying which for convenience have not been illustrated in theas the various altitudes in these routes, together with means forlighting lamps in those particular elevations of particular routes whichhave been authorized by the Airways Traflic Control oliice of the CivilAeronautics Commission to be occupied by a particular transport company.This ofilce is conveniently designated the ATC office.

Another object of the present invention resides in the provision ofmeans whereby these indicating lamps may be lighted distinctively toindicate either advance clearance which signifies that a particularroute through particular altitudes has been tentatively assigned by theATS ofi'ice to a particular air transport company and to light suchlamps in a different distinctive manner to signify that actual clearancehas been given to such particular air transport company over suchparticular route and altitude.

Another object of the present invention resides in the provision ofmeans whereby if lamps have once been lighted to signify actualclearance by the ATC oirlce such clearance cannot be cancelled by theA'IC office but must be cancelled by the particular air transportcompany oflice for which actual clearance of such route has been given.

Another object of the present invention resides in the provision ofother distinctive lamps on the panels of each of the various competingtransport companies to signify that advance or actual clearance over aparticular route or routes at particular altitudes has been given to aparticular air transport company.

Another object of the present invention resides in the provision ofplane progress lamps conveniently also called token lamps on the panelslocated both in the ATO office and in the offices of the varioustransport plane companies to indicate the progress of a particular planeat a particular altitude over a particular route, these lamps beingcontrolled by an attendant in the office of the air transport companyconveniently called airline oflice which has been authorized to fly aplane over such route or routes.

Another object of the present invention resides in the provision ofelectrically interlocked circuits which are so interlocked that if theattendant at the A'I'C office should attempt to give advance clearanceover a route which is in conflict with a route over which either advanceclearing or actual clearing has already been given it will prevent himfrom giving either advance clearance or actual clearance over theproposed route.

Another object of the present invention resides in the provision oftiming means for removing the restriction, or interlocking feature, im-

posed on an initial portion of a route, a specific time after such routewas reported occupied, as signified by the lighting of a lamp located inthe ATC ofiice by an attendant at the ofiice of the transport planecompany which has been authorized to travel over such particular route,such lamps preferably being located in the ATC office and in each of theair transport ofiices. This is considered safe because airplanes have aspecific minimum speed limitation in order to maintain altitude and itmay therefore be assumed that a plane has travelled a minimum specificdistance in a particular time.

Another object of the present invention resides in the provision ofmeans to render this interlocking feature at times, as under clearweather conditions, inactive.

Other objects, purposes and characteristic features of the presentinvention will be apparent from the description which follows whenconsidered in the light of the accompanying drawings of which Figs. 1A,1B and 1C illustrate the panel located in the ATC oifice of oneparticular route which is crossed by another route illustrated by asimilar panel shown in Figs. 1D, 1A and 1E.

Figs. 2A, 2B, 2C, 2D, 2E, 2F and 2G illustrate the circuit wiringextending between the ATC office illustrated in Figs. 20, 2D, 2E, 2F and2G and the panels of the American Transport Company oflice illustratedin Fig. 2A and the panel at the Eastern Air Transport ofiice illustratedin Fig. 2B for eastbound routes at elevations of 5000 and 7000 feet andfor westbound elevations of 4000 and 6000 feet between check points Qand R illustrated in Fig. 1D of the drawings; and

Fig. 3 illustrates the electrically interlocked circuits at the ATCofiice only for the point at which the two airplane routes cross eachother, as illustrated in Fig. 1A, at the 7000 foot elevation, thesecircuits also illustrating that not only is this a crossing point of tworoutes but is a point at which a plane may change its travel from oneroute to another crossing the same, the circuits for controlling thecorresponding lamps at the air transport company offices and circuitswhich show the manner in which the plane progress lamps or token lampsare controlled (see similar circuits in Figs. 2A, 2B and 20) have forconvenience been omitted.

Referring to Figs. 1A to 1E, inclusive, attention is directed to themulti-elevation airplane route illustrated in Figs. 1A, 1B and 1C whichextends from check point C to check point J, with the provision ofintermediate check points D, E, F, G, H and I. This route has been solaid out on the panel in the ATC office that check points D, G and Jlend themselves to constitute airports, that is, at these points D, Gand J, airplanes may actually rise from the ground and may descend tothe ground or rise into the stratosphere or descend from thestratosphere, whereas between check points E and F, H and I airplanesmay only fly at constant elevations.

The circuits associated with the apparatus lo cated in the ATC olficeare of the entrance-exit type, that is, these circuits are so organizedthat by operating an entrance knob, button or lever at a particularcheck point and operating an exit knob, button or lever at the nextcheck point circuits will be established to light lamps on the ATC panelwhich visually indicate a flight route extending from one elevation atthe first check point to the same or a difierent elevation at the nextcheck point. The entrance control knobs or buttons have been designatedby the letter N with a suitable prefix number signifying the altitude ofthe route and having a sufi'ix letter signifying the check point.Referring to Fig. 1A, for instance, the entrance knob 'lNC signifiesthat this is the entrance knob for the 7000 foot altitude at the checkpoint C, whereas the exit knob 5XD signifies that this is the exitpointof a route terminating at check point D at the 5000 foot altitude. Theentrance and exit knobs at other check points and other altitudes havebeen similarly designated.

In order to illustrate how the attendant in the ATC oftlce may signify aparticular route on his control panel, and also on the indication panelsof the air transport companies which fly over such routes and which arefragmentarily shown in Figs. 2A and 2B, let us assume that he wishes tostart an airplane at the airport located at check point D and that hewishes to continue the fiight of this plane at a 7000 foot elevation atcheck point T on another route which crosses the route C to J. In orderto set up this route to signify advance clearance he will operate theentering button llNDE (signifying entrance of a plane at zero elevationat check point D in an easterly direction) followed by the depression ofthe exit knob or button 'IXE. The operation of these two control buttonsONDE and TXE, in the order given, will cause the lamp in the entrancebutton GNDE to be lighted and further will cause the ascending lamp 53Land 54L for the block from check point D to check point E to be lightedand further causes the exit lamp 'IXEL to be lighted as shown in Fig.1A. Th attendant at the ATC ofiice will next operate the entrance buttonENE (see Figs. 1A and 3) for east-west route and the exit button TXS(see Fig. 1E) for the north-south portion of the crossing route, so thata route is established starting at check point E and ending at checkpoint S for the 7000 foot elevation as is signified by the illuminationof the lamp in the entrance button 'INE and by the illumination of theexit lamp IXSL (Figs. 1A and 1E). The attendant at the ATC omce willnext operate the entrance button INS (see Fig. 1E) followed by theoperation of th exit button 'lXT. This will result in the illuminationof the lamp in the entrance button INS and in the illumination of theexit lamp 'l'X'IL.

In order to illustrate how another route may be set up at the same timeover portions of the same radio beam but at a different altitude withoutconflict with the route just traced, let us assume that the attendant atthe ATC office has been informed that there is a plane arriving at pointQ (see Fig. 1D) at the 7000 foot elevation and that this plane desiresto pass over the check point S. Since the crossing point 39 is alreadyoccupied at the 7000 foot altitude it would be impossible to set up aroute extending to the check point S at the 7000 foot altitude by reasonof interlocked circuits described hereinafter so that the attendant willbe compelled to operate his buttons to allow travel of the plane underconsideration over the crossing designated by points 3'! to 44,inclusive, at a different altitude. In view of these circumstances theoperator will operate the entrance knob INQ (Fig. 1D) and will followthis by the operation of the exit knob 5XR. The operation of these knobs'INQ and 5XR will result in the illumination of the lamp in the entrancebutton 'INQ, the descending lamp 5 IL for the block Q--R and will resultin the illumination of the exit lamp SXRL. The attendant at the ATCofiice may now operate the entrance button N3. and follow this by theoperation of the exit button 5X8. The operation of these two buttons,providing no route in conflict has already been set up, will result inthe illumination of the lamp in the entrance button ENR and in theillumination of the exit lamp EXSL. The operator may now, if he sodesires, continue the flight of this plane, and give indications of itsauthorization, at the 5000 foot elevation in the block extending beyondcheck point T by operation of the entrance button ENS (see Fig. 1E)followed by the operation of the exit button 3XT. The operation of thesebuttons 5N S and EXT will result in the illumination of the lamp in theentrance button 5N8, the descending lamp 52L for the block S--T and inthe illumination of the exit lamp 3XTL.

It may be pointed out at this time that the entrance knobs or buttons Nare turn buttons which may be turned to a particular position to signifya particular transport company tentatively or actu ally authorized andthe exit knobs X are spring return push buttons which may be depressedand released to perform the exit function, all in a manner as more fullyapparent when the circuits illustrated in Fig. 2 are describedhereinafter.

It may also be pointed out here that certain plane progress or tokenlamps illustrated by a circle, having adjacent thereto a tokenreceptacle represented by a square, are employed. These token lamps onthe board at the ATC office, as more fully described hereinafter, arecontrolled from the oifice of the transport companies and if desired theattendant at the ATC office may insert a token in the receptacleillustrated by a square to signify the particular plane which has beenreported to be located at the particular point corresponding to thepoint where the token lamp illuminated is located. As illustrated thesetoken lamps are located on horizontal portions of the route and are alsolocated on descending and ascending portions of the route.

As more fully pointed out hereinafter if, for instance, the token lamp Lfor the block Q-R (see Fig. 1D) becomes lighted, in response tomanipulation of control button '10 on the panel located in the transportoflice, the lamp in the entrance button 'INQ will be extinguishedwhereas the lamps ML and 5XRL will remain lighted, all

in a manner more specifically described hereinafter. Although this lampin the entrance button 1N6} is extinguished this button TNQ will not beavailable for allowing a second route entering at that point andaltitude to be established until a predetermined time, measured by asuitable time element device described hereinafter, has elapsed. Thatis, the release is time delayed. Additional provision is made forsuccessively extinguishing the ascending lamps, such as, 50L and 55L ofblock Q--R (see Fig. 1D) and such as the descending lamps 50L and 5 ILfor the block Q-R illustrated in this same figure and located in the ATCoffice by suitable manually controlled pushand-pull buttons located inthe air transport company oiiices. sending and descending lamps as wellas the entrance lamps and exit lamps are lighted by the attendant in theATC office and are extinguished by the attendant in one of the airtransport company omces.

Referring now to Fig. 2A of the drawings, it will be seen that the 4000,5000, 6000 and 7000 foot altitudes for the block QR (see Fig. 1D) havebeen reproduced in the American Airline office designated by the letterAA and referring It therefore follows that these as toFig. 213 it willbe seen that a similar panel has been illustrated in the Eastern Airlineomce, des ignated by the referencccharacter EA, for the 4000, 5000, 6000and 7000 foot altitudes for the route of the block Q-R. It is to beunderstood that the lamps illustrated in the entrance knobs in the ATCoffice (see entrance knob TNQ of Fig. 1D) have been designated byreference charactors, such as, 'IAQ in the. American Airline ofiice ofFig. 2A and have been designated by reference characters, such as, TEQin the Eastern Airline office illustrated in Fig. 2B. The exit lampssuch as 'EXRL (see Fig. 2A) and the exit lamp IXRL (see Fig. 28) havebeen designated by the same reference character as has the exit lampIXRL in the ATC office (see Fig. 1D). Similarly, the plane progressindicating or token lamps, the ascending and the descending lamps in theair transport offices AA and EA (see Figs. 2A and 213) have beendesignated by the same reference characters as has been applied tosimilar token lamps and ascending lamps and descending lamps on thepanels in the ATC ofiice (see Fig. 1D). The token lamps illustrated inthe airline ofiices AA and EA (see Figs. 2A and 2B) are located withinpushand-pull buttons such as push-and-pull button 12 for the token lamp12L (see Figs. 2A and 2B), These pushand-pull buttons if pushed in willbe retained in that position and if pulled out will be retained in suchposition.

Figs. 1A, 1B and 1C should be laid end to end in that order with Fig. 1Dlaid below Fig. 1A and Fig. 1E laid above Fig. 1A to constitute adrawing of the panel located at the ATC ofiice and these willhereinafter collectively be referred to as Fig. 1. Referring to Fig. 1the entrance buttons, such as entrance button 'ENQ (see Fig. ID), arecombincd rotary and push buttons which are provided with a light in theknob thereof, the rotary con tacts being shown in Fig. 2D and beingdesignated by the reference characters and 00 and the push contact beingdesignated by the reference character 0?. The exit button (see Fig. 2G)is a spring return push button and for the same straight through routeat 7000 feet elevation, in the block Q-R in Fig. 2G of the drawings hasbeen designated 'EXR (see also Fig. 1D).

For simplicity the circuits for controlling between the 3000 footelevation and the 8000 foot elevation of the block Q-R (see Fig. 1D)only have been illustrated in Figs. 20, 2D, 2E, 2F and 2G it beingunderstood that the circuits for similar apparatus, since they areidentical and have for convenience been omitted, need not beillustrated. Referring again to Fig. 1D the sloping substantiallyvertical lines in this figure show by the illumination of lamps that aparticular plane is to change its altitude, the plane lowering itsaltitude if the arrows point downwardly and increasing its altitude ifthe arrows point up wardly. The rectangles shown in the sloping verticallines and containing arrows signify lamps which have been identified bythe reference characters L, L, 52L, 53L, 54L, 55L, 50L, 51L, 58L, 59L,00L, BIL, 62L and 63L. These lamps are located at points where a planeflying in one direction is making an ascent or a descent when crossing aroute for planes flying in the opposite direction. In other words, theselocations, such as the location of lamp 50L, show a crossing point oftwo routes, whereas the crossing points illustrated by heavy dots 2!,22, 23, 24, 25, 26, 2?, 20, 29, 3!, 32, 33, 34, 35 and 36 illustratecrossing points of air routes for planes flying in one particulardirection only and therefore constitute not only crossin points butconstitute points where a plane may change from a horizontal directionof movement into an ascending or descending route or may move from anascending or descending route into a horizontal route. In order toclearly disclose the relationship of the various relays to the routes,that portion of the diagram illustrated in Fig. 11] containingconverging-diverging route elements designated by points 23, 24, 25, 26,3|, 32, 33 and 34 have been illustrated by heavy linesin Fig. 2. It maybe pointed out here that Fig. 2 constitutes Figs. 2A and 2B laid undereach other with Figs. 2C, 2D, 2E, 2F and 2G laid side by side in thatorder to the right of Figs. 2A and 2B.

Referring now to Fig 2 it will be seen that each of theconverging-divergin points 23, 24, 25, 26, 3!, 32, 33 and 34 hassuitable reference characters applied to the route portions convergingto such point and diverging from such point. For convenience theconverging or entering route portions have been designated EN and ERwhere the reference character E represents entering, the referencecharacter N represents normal (horizontal), and the letter R representsreverse (meaning inclining or declining). The diverging route portionshave been designated DN and DR, the letter D meaning departing so thatthese reference characters signify departing normal and departingreverse, respectively, the letter N again signifying horizontal and theletter R signifying reverse, that is, ascendor descending.

The entrance-exit type of network employed in the present inventionrequires a special relay for each converging point which, forconvenience, has been designated YR with a prefix corresponding to thepoint at which it is located. In addition to the relay 23YR. for point23 there is provided for each of the route portions a relay designatedby the reference character of that route portion which is preceded by aprefix corresponding to the point at which the relay is located. Inother words, these relays have been designated 23EN, 23ER, 23DN and23DR. Similar relays are provided for each of the converging-divergingpoints 24, 25, 26, 31, 32 33 and 34, and these relays are preferablyinterconnected as illustrated in Figs. 2D, 2E, 2F and 2G 01 thedrawings. In addition ,to these relays there is provided an exit relaydesignated 'IXRR for the exit point containing push button 'IXR,similarly designated relays being provided for other exit points. Foreach exit relay, such as 'IXRR, there is provided an exit repeater relaysuch as 'IXRP.

Each entrance button. such as entrance button 'INQ, is provided with atiming relay TR, an advance clearance relay GR and a final clearancerelay CR, each reference character of which is preceded by a prefixcorresponding to the prefix associated with such entrance button. Thetiming relay TR is of a construction so that when deenergized itscontacts will immediately assume the open position and which ifreenergized will not reclose these contacts until after the expirationof a predetermined period of time which may, for instance, be tenminutes. This period of time is selected in accordance with localconditions such as the speed of th planes employed, the density oftraffic and the like, the purpose of this timin device being to preventa second plane from following a first plane over a particular route lessthan a safe distance determined by the period of time between planestarting presumed to be ten minutes for the system under consideration.

Each of the entrance buttons is provided with an AP relay and an EPrelay in the particular construction illustrated, it being assumed thatthe ATC oiiice illustrated in Fig. 2C-2G is connected only to two airtransport companies, such as the American Airline ofiice illustrated inFig. 2A, and the Eastern Airline oflice illustrated in Fig. 23. That is,only these two transport companies fly over the routes illustrated. Therelay TAP is more particularly associated with the American Airlineofiice, whereas the relay EP is more particularly associated with theEastern Airline ofiice. These relays AP and EP are controlled by thecontact 45 of the associated entrance button. In other words, theentrance button 'INQ through the medium of its contact 46 controls therelays TAP and 'lEP, there being similar relays for the contact 45 ofother entrance buttons, some of which have not been illustrated in thedrawings.

In each of the air transport offices is provided a similar panel to thepanel illustrated for the ATC omce in Fig. 2D-2G, but for convenienceonly a small portion of each of these panels has been illustrated inFigs. 2A and 23, respectively. The portion of these panels illustratedin Figs. 2A and 2B is that portion of these panels which represents theair traific route in the block Q-R for the altitudes of 4000, 5000, 6000and 7000 feet and also the portions representing the ascending anddescending routes associated therewith. In place of the entrance buttonINQ illustrated in Fig. 2D of the drawings there is provided a lampdesignated IAQ for the American Airline ofiice in Fig. 2A of thedrawings and a lamp TEQ for the Eastern Airline ofiice illustrated inFig. 2B of the drawings. The exit lamp for each route, such as the exitlamp 'IXRL in Fig. 2G of the drawings has been illustrated in a likemanner and has been designated by the same reference character IXRL atboth the American Airline ofice illustrated in Fig. 2A and the EasternAirline oflice illustrated in Fig. 2B.

Similarly, the lamps for descending routes and designated ML and 52L inFig. 2D of the drawings have been reproduced on the panels in theAmerican Airline ofiice and the Eastern Airline office by a similarconventional showing and designated by the same reference characters MLand 52L in both Figs. 2A and 2B of the drawings. Similar lamps beingprovided for other ascending and descending routes. Also, theconvergingdiverging route points 23, 24, 25, 25, 3|, 32, 33 and 34illustrated in Fig. ID of the drawings and also illustrated in Figs.2D-2G of the drawings have also been illustrated and similarlydesignated in Figs. 2A and 2B of the drawings.

It may be pointed out at this time that the entrance lights, the exitlights, and the ascending and descending lights illustrated by arrows ineach of the three oflices (ATC office, American Airline ofiice, andEastern Airline ofiice) are controlled from the ATC ofiice illustratedin Figs. 2C-2G, Whereas the token lights or plane progress lights, suchas 10L, 12L, 13L, 18L, 19L, L, 8iL, L, 86L and 93L illustrated in Figs.1]), 2A, 2B, 2D, 2E, 2F and 2G are controlled from the air transportofiices illustrated in Figs. 2A and 2B. In fact, as illustrated thesetoken lamps constitute push-and-pull contact controlling buttons whichfor the lamp 12L has been designated 12, and which control relays KA,which for the token lamp 12L and the push-and-pull button 72 have eendesignated 'IZKA! and TZKAQ, there being similar relays for each of theother token pushand-pull buttons for the American Airlines oflice shownin Fig. 2A and similarly the buttons for the Eastern Airline oiflceshown in Fig. 213 have been assigned like reference characters exceptfor the substitution of the letter E for the letter A. The token lamps,such as, 12L, 53L and 93L just mentioned, are associated with ascendingand descending route portions, whereas token lamps "IL, "L, 18L, 19L,80L and (ML are associated with horizontal air routes. It should benoted that the token relays KA and KE control token repeater relaysdesignated KR and KP located in the ATC oflice. The relay iKRi (see Fig.20) located in the ATC offlce may be controlled by either the tokenrelays l8KAl and 13KA2 located at the American Airline oflice (see Fig.2A) or may be controlled by the token relays IBKEI and I8KE2 located inthe Eastern Airline oflice illustrated in Fig. 213. Other token repeaterrelays KR are controlled in a similar manner. The token repeating relaylZKP, for instance, may be controlled through the medium of thepush-and-pull button 12 and relays EZKAI and IZKAZ shown in Fig. 2A ormay be controlled by the pushandpull button 12 and the token relays72KB! and 12KE2 illustrated in Fig. 2B. Other KP relays are controlledin a similar manner.

Each of the KR relays and KP relays illustrated in Fig. 2C is providedwith a repeater relay of the double winding neutral type which has beendesignated M. The letter M signifying momentary deenergization. Theserelays M are neutral relays but are provided with two windings which areso connected in the circuit as to'polarity that one of these windingswhen energized magnetizes the magnetic structure of the relay in onedirection, whereas the other winding when energized magnetizes thisstructure to the opposite magnetic polarity. One of these windings isenergized when the associated KB. or KP relay is energized, whereas theother winding is energized when such relay KR or KP is in itsdeenergized position. The obvious result which follows is that for eachpicking up and each dropping of a KR relay or a KP relay its associatedM relay is energized by current of the opposite polarity to that whichit was previously energized so that the magnetism in its magneticstructure must pass through zero as a result of which the front contactof the M relay is momentarily opened for each change in the position ofan associated KR relay or KP relay. This structure is resorted to tocause momentary opening of a circuit for the purpose of dropping stickrelays under certain conditions, all in a manner as more specificallypointed out hereinafter.

In the American Airline oihce illustrated in Fig. 2A there are alsoprovided repeater relays for the exit repeater relays lXRP and 'EXRPillustrated in Fig. 2E of the drawings, these repeater relays have beendesignated TXRPA and SXRPA, respectively, there being similar relaysiXRPE and EXRPE for the panel of the Eastern Airline office illustratedin Fig. 2B. These relays TXRPA and DCRPE directly repeat the relay TXRPshown in Fig. 2E, whereas the relays EXRPA and EXRPE shown in Figs. 2Aand 23,

respectively, directly repeat the exit repeater relay I XRP illustratedin Fig. 2E of the drawings.

Also, the condition or energization of the relays 23DR and ZEiERillustrated in Fig. 2D of the drawings is repeated in theAmerican andEastern .Airline offices, respectively, by the relays TDRPA in theAmerican Airline oifice illustrated in Fig. 2A and by the relay 'IDRPEin the Eastern Airline ofiice illustrated in Fig. 2B. In a similarmanner, energization of the relays 25DR illustrated in Fig. 2D and therelay ZIER (not shown) is repeated in the American Airline office by therepeater relay SDRPA (see Fig. 2A) and is repeated into the EasternAirline oflice by the relay EDRPE (see Fig. 2B). Each of these relays'IDRPA and EDRPA of Fig. 2A and IDRPE and EDRPE of Fig. 23 whenenergized signify that a descending route has been set up at pointscorresponding to these relays by the control apparatus in the ATC ofliceillustrated in Figs. 2C-2G.

Some of the indicating lamps for the main control panel in the ATCoffice illustrated in Figs. 2C-2G as well as some of the lampsillustrated in the American Airline office in Fig. 2A and on the panelfor the Eastern Airline oi'ilce illustrated in Fig. 2B are at timesenergized by steady light to give continuous illumination and are atother times energized intermittently to produce flashing illumination ofthese lamps. In order to illustrate interrupted energy as distinguishedfrom the steady energy the legends flashing and steady have been appliedto the tail ends of suitable arrows illustrating a source of current inFigs. 2A, 2B and 20 of the drawings.

As already mentioned the circuits for controlling the indicating lampsboth on the ATC board shown in Figs. 2D-2G and on the two transportcompany boards shown in Figs. 2A and 23, respectively, are sointerlocked that a second route in conflict with an already authorizedroute cannot be set up. This interlocking feature is proposed to beeffective only when the apparatus is operated under instrument flightrules. In this connection it may be pointed out that commercialairplanes fly under two sets of rules, namely, instrument flight rulesand contact flight rules. By instrument flight rules is meant rules thatare considered safe under blind flying conditions, such as night flying,and flying in conditions of severe fog. By contact flight rules is meantrules that prevail when vision is sufficiently good to assure a pilotfollowing the radio beam against colliding with another plane. In orderto have the apparatus disclosed function under these two flight rulesconditions a lever (see Fig. 2E) is provided in the ATC oflice which isnormally, as illustrated, assuming the instrument flight rule positionwith the contact associated therewith open. If this lever is moved tothe contact flight rule position an energizing circuit for the relay FCRis closed by this contact. With relay FCR energized energy is removedfrom all ER and DR relay stick circuits by the opening of back contact96 of this relay FCR (see Fig. 2C). Also, with this relay FCR energizedthe timing relays, such as lTR and 5TB are held permanently energizedthrough the medium of front contacts 98 and 91' of this relay FCR.Furthermore, with this relay FCR energized repeater relays FCRPA (seeFig. 2A) and relay FCRPE (see Fig. 2B) are energized through frontcontact as of relay FOR. These relays FCRPA and FCRPE are located in theoflices of the American Airline oflice and the Eastern Airline oflice,respectively. The instrument flight rule lamps 66 controlled by therelays FCRPA and FCRPE, are normally energized through back contacts 6-!of these relays and upon movement of the lever .95 in the ATC office toits contact flight rule position these indicating lamps 66 in the airtransport tact H5 and its front contact H6. of the stick contact H5closes a stick circuit for offices are extinguished and in place thereofthe contact flight rule lamp 1'9 is energized. In order to get a betterunderstanding of the entire system, and particularly the entrance-exittype interlocked circuits, operation of a portion of the system will nowbe discussed.

Operation I Let us assume that the attendant at the ATC offioe shown inFigs. 1D, 2D, 2E, 2F and 2G is operating under instrument flightconditions, that is, the lever 95 (see Fig. 2E) assumes its right-handposition and that the attendant intends to set up a flight routestarting at the 7000 foot elevation at check point Q and terminating ata 5000 foot elevation at check point B as illustrated by lighted lampsin Fig. ID of the drawings. Let us further assume that this route is tobe used by the American Airlines Company rather than by the EasternAirlines Company, the panels of which are shown in Figs. 2A and 2B,respectively. In order to set up this route the operator will turn hisentrance button 'INQ (see Fig. 2D) toward the left as indicated by thearrow point projecting from this button in Fig. 1D of the drawings. Thisturning of the entrance button 'INQ causes closure of a circuit at onepoint by contact 46 and causes closure of a circuit for the relay 23YRat contact 45 (see Fig. 2D). The completion of this last mentionedcircuit through back contact I of relay 23ER energizes the relay 23YRand establishes two circuits beyond the contact IilI of relay 23YR.

The first of these circuits extends through front contact IOI of relay23YR through back contact I02 of relay 23DR, wire 382, and back contactIE3 of relay 24ER to the winding of relay 24YR, whereas the othercircuit extends through front contact IIlI of the relay 23YR throughback contact I 84 of relay 23DN. wire 432, back contact I05 of relayGXQP, wire 442, through back contact Iflii of relay 25EN, through backcontact IGI of relay 25YR, through back contact I62 of relay 25DR, wire45Z, and back contact I83 of relay 26ER, through the winding of relay283KB, as a result of which both of the relays 243KB. and ZfiYR areenergized and picked up. The picking up of relays 24YR and 26YRestablish new circuits through front contacts H0 of relays 24YR and'ZEYR and wires 5ZZ, 53Z, 6:22 and 652 extending to associated exitrelays 'IXRR. and SXRR. It is thus readily seen that either the exitrelay 'IXRR or the exit relay EXRR may be energized by depression of therespective exit buttons 'IXR and EXR. Since the route proposed to be setup starts at the entrance button 'INQ and ends at the exit button 5XR(see lighted lamps in Fig. 1D) the exit button 5XR will now be assumedto be depressed.

Depression of the exit button EXR (see Fig. 2G) will cause the circuitheretofore traced up to and including the front contact IIi! of relayZISYR to be continuedthrough back contact H2 of relay 26DR, wire 65Z,through back contact N3 of relay 33DR, wire 142, through back contactII4 of relay 32DR, through the winding of the relay BXRR, and exit pushbutton contact EXR to the terminal of the same source of current, theterminal of which is connected to the contact 45 of the entrance buttonTNQ. The completion of this circuit will, of course, cause the exitrelay EXRR to pick up to close its stick con- The closure the relay EXRRso that the exit push button EXR may be released.

Closure of the front contact I I6 of relay BXRR. closes an energizingcircuit for the exit repeater relay SXRP through wire Ii'IZ resulting inthe picking up of this latter relay. With the exit repeater relay EXRPnow picked up the following stick circuit is closed to maintain thisexit repeater relay EXRP energized: beginning at the terminal backcontact 96 of the relay FCR (see top of Fig. 20), front contact I20 ofthe relay M associated with the relay 5KR2, front contact I2I of therelay M associated with the relay EKRI, the contacts I20 and I2I havingin multiple therewith front contacts H8 and H1 of relays 5XR2 and BXRIin multiple, wire 34Z, and stick contact I22 included in series with thewinding of the relay BXRP and to the other terminal of the same source.Also, with the repeater stick relay SXRP now energized the lamp 5XRL(see Figs. 1D and 2E) is energized through front contact I23 of therelay 5XRP. This contact I23 also closes an energizing circuit includingwire IZ for the relays SXRPA and SXRPE (see Figs. 2A and 23,respectively) which in turn through the medium of their front contactsI24 close energizing circuits for the exit lamps EXRL shown in Figs. 2Aand 213, respectively.

With the exit repeater relay SXRP (Fig. 2E) now energized and maintainedenergized by a stick circuit the closure of its front contact I26 closesan energizing circuit for the departing normal relay ZBDN including backcontact I21 of the relay 26DR. The closure of this circuit results inthe energization of the departing normal relay ZGDN which through themedium of its front contact I28 now closes an energizing circuit for theentering normal relay 26EN including the front contact I29 of relay ZBYRand back contact I39 of entering reverse relay ZGER. With the enteringnormal relay 26EN now picked up an energizing circuit for the departingnormal relay 25DN including the front contact I3I of entering normalrelay 26EN, wire 462, and back contact I32 of the departing reverserelay 25DR, is closed. The picking up of the departing normal relay 25DNby closure of its front contact I33 closes an energizing circuit for theentering reverse relay25ER including back contact I34 of relay 25YR andback contact I35 of entering normal relay 25EN. The picking up of theentering reverse relay ZSER through the medium of its front contact I36closes an energizing circuit for the departing reverse relay 23DRincluding the back contact I 31 of the departing normal relay 23DN. Thepicking up of the departing reverse relay 23DR through the medium of itsfront contact I38 closes an energizing circuit for the entering normalrelay 23EN including the front contact I34 of relay 23YR and backcontact I40 of the entering reverse relay 23ER.

The picking up of the departing reverse relay 23DR also at its backcontact I02 interrupts the energizing circuit including wire 38Z for therelay 24YR so as to remove energy from one terminal of the exit relay'IXRR so that depression of the exit button 7XR will no longer produceany result. In a similar manner, the picking up of the exit repeaterrelay 5XRP by the opening of its back contacts MI and I42 has brokencertain interlocked circuits including wires BIJZ, BIZ, Hz and 63Z toprevent conflicting airplane routes for west-bound plane movement beingvisually established. Also, the picking up of the departing normal relayZGDN by the opening of its back contact I43 in wire 662 prevents aconflicting route for east-bound plane movement being set up. Thepicking up of the departing normal relay 25DN by the opening of its backcontact I04 in wire 502 prevents the establishment of a conflictingroute visually on the boards at the ATC office and at the two airtransport offices. The picking up of the reverse entering relay Z'SER bythe opening of its back contact IIIII prevents the relay 25YR beingpicked up by the entering knob 5NQ from which it is apparent that noroute originating at the entrance knob 5NQ can be visually establishedon the panel. Also, the picking up of the entering normal relay 23EN bythe opening of its back contact I06 in wire 312 interrupts a circuit foranother conflicting route starting at a point signifying a higheraltitude 'fo'r east-bound flying.

The relays 5XRP, 26DN, ZBEN, 25DN, 25ER, 23DR and 23EN are nowenergized, for each of these relays except the last mentioned one thereis provided a stick circuit of which the closed stick circuit for therelay 'SXRP has already been traced. Each of the stick circuits for exitrepeater relays, such as relay SXRP, is normally closed at all pointsexcept at the stick contact. The departing normal relay ZGDN has itsstick circuit including its stick contact I50 closed at front contactI5I of the exit repeater relay SXRP. In a similar manner the enteringnor- 25DN has its stick circuit including its stick contact I54 closedat front contact I55 of the entering reverse relay 25ER, and'in'multiple therewith by the front contact III of the entrancenormalrelay 25EN if this latter relay were up. The relay 25EN does not haveits stick circuit including wire 36Z and back contact I'III of timingrelay 5TB closed for two reasons, first, because its stick contact I33is open, and secondly, because the timing relay 5'IR assumes itsenergized position. The departing reverse relay 23DR and the enteringreverse relay 25ER have their stick circuits including stick contactsI66 and I61 and wire 322 closed at front contact I68 of the relay Massociated with the relay I2KP and at front contact I89 of such relay12K? in multiple therewith (see Fig. 2C) and also including back contact96 of the relay FCR in series therewith. From this latter stick circuitit is readily seen that picking up of the relay 'I2KP as, for instance,by the depression of the button I2 in the American Airline officeillustrated in Fig. 2A. will cause the stick circuit to be shifted fromthe front contact I68 to the front contact I69 of the relay 'IZKPwithout opening of the stick circuit. It is also readily seen that upondeen'ergization of the relay 'IZKP due to the pulling out of this buttonI2 its front contact I69 will be opened followed by momentary opening ofthe front contact I68 of the associated M relay. This momentary openingof 'the contact 168 of the relay M due to dropping of the relay 12K?will cause momentary opening of the stick circuit for the relays 2333B.and Z-EER and the dropping of these relays.

The lat er of which when dropped will open the 1 somewhat differentstick circuit and this relay would drop as soon as its pick-up circuitincluding the contact 45 of the entrance button INQ and the indirectstick circuit including the front contact I of the final clearance relay10B are both opened. Since, however, the entering normal relay 23EN isslightly slow dropping, as conventionally shown, its stick circuitincluding stick contact I83 and back contact I'Ill of timing relay willbe closed before this relay ZBEN begins to drop. The energization ofthese various entrance and exit relays will cause the indicating lamps5IL and EXRL (see Figs. 1D, 2D and 2G) to be lighted, the lamp 5IL inthe ATC office being lighted through a circuit including front contactI86 of the relay 23DR and contact I8 of relay 25ER in series whereas therelays 'IDRPA and 'IDRPE in ofiices AA and EA are energized throughthese same contacts and wire 42, (see Fig. 2D). Also, the exit light5XRL in the ATC ofiice is energized through a circuit including thefront contact I23 of the exit repeater relay 5XRP (see Fig. 2E), whereasrelays EXRPA and EXRPE in oflices AA and EA are energized through thissame contact I23 and wire 12.

With the entering normal relay 23EN now energized in a manner as justdescribed its closed front contact I63 estabishes an energizing circuitthrough wire 29Z for the advance clearance relay 'IGR. (see Fig. 20).With this advance clearance relay IGR now assuming its energizedposition its closed contact 224 completes an "energizing circuit throughwire ZIZ for the lamp 225 located in the entrance button 'INQ and causesit to be lighted through a circuit energized by steady current andincluding back contact 226 of the final clearance relay ICE and thefront contact 22'! of the timing relay ITR (see Fig. 2C), so that theentrance knob lNQ appears illuminated as illustrated in Fig. ID of thedrawings. The lamps 225 located in button INQ and the lamps BIL and SXRLare now lighted, as conventionally shown in Fig. 1D of the drawings,thereby informing the attendant at the ATC ofiice that he hastentatively assigned this route to a particular air transport companywhich in practice is called the giving of advance clearance.

Let us now observe how such advance clearance is distinctively indicatedin the two air transport ofiices illustrated in Figs. 2A and 213,respectively. With the entrance button for the 7000 foot elevationbetween check points Q and R moved to its upper position (see Fig. 2D)the closed contact 46 establishes an energizing circuit for the relay'IAP which circuit may be traced as follows: beginning at the terminalof a suitable source of current, front contact I16 of the timing relay'ITR, front contact III of the advance clearance relay 1GB, wire I'SZ,contact 46 of the entrance button 'INQ, wire IBZ, winding of the relay'IAP, through back contact II-Z of the relay 1E1, to the terminal of thesame source of current. The closure of this circuit will result in thepicking up or" the relay 'I-AP and in the energization of a circuit forthe relay 'IAR located in the American Airline office illustrated inFig. 2A by current of positive polarity through the front contact I13 ofthe relay IAP and wire 82A. It will also result in the energization of acircuit by current of negative. polarity for the relay 'IER. located inthe Eastern Airline ofiice illustrated in Fig. 2B of the drawingsthrough the medium of contact IN of the relay TAP and wire 82E. Theopposite terminal

